One known hybrid integrated circuit device is a high-frequency power amplifier module which is used for the wireless communication section of mobile communication units such as automobile telephone units and portable telephone units.
Japanese Patent Unexamined Publications No. Hei 8 (1996)-148597 and No. Hei 9 (1997)-18145 describe hybrid integrated circuit devices.
The patent publication No. Hei 8 (1996)-148597 describes semiconductor modules of LGA (Land Grid Array) type.
The patent publication No. Hei 9 (1997)-18145 describes a technique for preventing cracks from occurring in a ceramic multi-layer substrate, from its positions at the rim of electrode terminals into the inside of substrate, based on the fabrication process, prior to the annealing process, of forming the electrode terminals on the surface of a laminated green sheet, and thereafter laminating a patterned greed sheet (a greed sheet with the formation, at its positions confronting the electrode terminals, of through-holes having a diameter smaller than the electrode terminals) on the laminated green sheet while leaving small areas of electrode terminals.
The high-frequency power amplifier module used for the portable telephone unit is amid the technical progress in terms of size reduction and performance upgrading. A high-frequency power amplifier module is mounted on a setup board (circuit board) by soldering the electrode terminals (connection terminals), which are located at the bottom edge of module, to the lands on the surface of setup board. Specifically, the high-frequency power amplifier module is placed by being positioned on the setup board, and solder which has been already applied to the lands of setup board is heated (to reflow) so that the module terminals are soldered to the lands and fixed on the setup board.
In recent years, there is a growing trend of the LGA structure adopted for the high-frequency power amplifier module to meet the demands of size reduction, performance upgrading, increasing pins, and mount area reduction.
The inventors of the present invention have confirmed the following programs in regard to the LGA structure of the high-frequency power amplifier module designed for the portable telephone unit.
FIG. 24 is a schematic diagram explaining the faulty setup of a high-frequency power amplifier module revealed by the study conducted by the inventors prior to the present invention. A high-frequency power amplifier module has its substrate 1 made of a multi-layer ceramic wiring substrate, and electrode terminals 2 are formed on the rear surface to align along the edge of substrate.
The high-frequency power amplifier module is mounted (fixed) on a setup board 3 by overlapping the electrode terminals 2 on the lands (foot print) 4 formed on the upper surface of the board 3, and fusing (to reflow) solder 5 which has been already applied to the lands 4 and the surface of electrode terminals 2 so that the electrode terminals 2 are fixed by soldering to the lands 4. Although the figure shows only one electrode terminal 2, all electrode terminals formed along the edges around the bottom of the module substrate 1 are connected to the lands to complete the mounting of module.
However, it was found that this high-frequency power amplifier module develops cracks 6 in the module substrate 1 as shown in FIG. 24, resulting in a degraded reliability of the high-frequency power amplifier module.
The electrode terminals 2 and solder 5 are both metallic and therefore have a greater bonding strength than the bonding strength between the ceramic module substrate 1 and the electrode terminals 2. In addition, the ceramic module substrate 1 has a thermal expansivity coefficient of around 7×10−6/, while the setup board 3 is a glass-epoxy board (made of glass fiber and epoxy resin) having a thermal expansivity coefficient of around 16×10−6/, exhibiting a significant difference.
In consequence, due to the stress caused by the difference of thermal expansion and contraction between the setup board 3 and electrode terminals 2, the relatively fragile module substrate 1 is liable to develop a crack 6. The crack 6 starts at a position (point) subjected to a large stress and advances deep into the module substrate 1 as shown in FIG. 24. The dashed-line arrows in the figure indicate the direction of stress which causes the crack. The development of crack 6 can deteriorate the reliability of high-frequency power amplifier module.
The above-mentioned patent publication No. Hei 9 (1997)-18145 describes, as mentioned above, a technique for preventing cracks from occurring in a ceramic multi-layer substrate, from its positions at the rim of electrode terminals into the inside of substrate, based on the fabrication process, prior to the annealing process, of forming the electrode terminals on the surface of a laminated green sheet, and thereafter laminating a patterned greed sheet (a greed sheet with the formation, at its positions nearby the electrode terminals, of through-holes having a diameter smaller than the electrode terminals) on the laminated green sheet while leaving small areas of electrode terminals, however, it does not describe in detail the mechanism of crack development.
The inventors of the present invention have found a fact that cracks are liable to occur in the module substrate at its positions of the electrode terminals, at their positions close to the substrate edge, which are located close to the edges of both ends or sides of the module substrate. Namely, the development of cracks, which are liable at positions of the electrode terminals 2, in their portions close to the substrate edge, which are located close to the edges of the module substrate 1, can be alleviated by coating these portions at least with a protection film.
In regard to the above-mentioned conventional technique, i.e., overlapping of a green sheet, with through-holes which are smaller in diameter than the electrode terminals being formed, at positions confronting the electrode terminals, and subsequent annealing, it is necessary for the sake preventing the damage in the edge section to make wide edge section where the through-holes are narrowest, resulting in a larger green sheet and thus an increased size of high-frequency power amplifier module.
Moreover, the green sheet with through-holes overlapped on another green sheet necessitates marginal dimensions so as to ensure the covering of the rim of electrode terminals, results in a much larger green sheet.
Therefore, the conventional technique based on the overlapping of green sheet causes an increased dimensions of green sheet, which precludes the reduction in the size of module board and thus the size of high-frequency power amplifier module.
A green sheet having through-holes needs to be thicker to some extent for the sake of damage-free treatment, and the use of extra green sheet material results in an increased cost of the module.
It is an object of the present invention to provide a hybrid integrated circuit device having high mounting reliability, and an electronic device which incorporates this hybrid integrated circuit device.
Another object of the present invention is to provide a hybrid integrated circuit device having high mounting reliability and having potential of manufacturing cost reduction, and an electronic device which incorporates this hybrid integrated circuit device.
Still another object of the present invention is to provide a high-frequency power amplifier module having high mounting reliability, and a wireless communication unit which incorporates this high-frequency power amplifier module.
Still another object of the present invention is to provide a high-frequency power amplifier module having high mounting reliability and having potential of manufacturing cost reduction, and a wireless communication unit which incorporates this high-frequency power amplifier module.
These and other objects and novel features of the present invention will become apparent from the following description and attached drawings.